If a voice recognition system is built for recognizing names of hotels and tourist facilities, a user may not know official names thereof, and it is thus conceivable to provide a plurality of names (paraphrased words) for one facility. For “Yokohama Prince Hotel”, for example, in addition to “Yokohama Prince Hotel”, names such as “Yokohama Prince” and “Prince Hotel” may be provided as a vocabulary to be recognized. This technology is described in JP 2005-202198 A (Patent Literature 1) and JP 2001-083982 A. (Patent Literature 2).
However, the voice recognition is generally realized by a pattern matching between a time sequence of feature vectors acquired by means of an acoustic analysis of a voice and a voice pattern model acquired by modeling a pattern of a time sequence of feature vectors of a vocabulary to be recognized, and if voice pattern models are provided for a large number of paraphrased words, there occurs a problem that a quantity of calculation for the pattern matching becomes enormous. There is another problem that even if paraphrased words are manually or automatically generated, it is difficult to generate all paraphrased words. There is still another problem that a large amount of labor is required for building rules and databases for the automatic generation.